M.A. Ertl:
"Forth Family Tree and Timeline";
in: "EuroForth 2004 Conference Proceedings", EuroForth 2004, 2004, 1 - 4.
http://aleph.ub.tuwien.ac.at/F?base=tuw01&func=find-c&ccl_term=AC04968566Electronic version of the publication:
http://www.complang.tuwien.ac.at/forth/family-tree/